The present invention is directed to telecommunication systems, and especially to call routing in telecommunication systems involving at least one internet protocol (IP) network. The present invention is especially advantageous in routing of special number calls in telecommunication systems involving at least one IP network. Examples of such special number calls is E9-1-1 calls for seeking emergency services and other abbreviated number calls for non-emergency special services, such as “N-1-1” systems. Examples of such N-1-1 systems include “3-1-1” (urgent but not emergency calls) and “5-1-1” (traffic inquiry calls). Special number calls may also include, by way of further example and not by way of limitation, abbreviated numbers for calling commercial services, such as “*820” (calling a radio station) or “GOTIX” (calling for tickets).
In the past, routing of calls using an internet protocol network—commonly referred to as Voice over Internet Protocol (VoIP) calls—has typically been carried out according to long established Public Switched Telephone Network (PSTN) rules. Following those rules, a VoIP switch uses the destination phone number's (i.e., the called party) area code and prefix to determine the appropriate PSTN gateway to which the call should be handed off. The area code and prefix is sometimes referred to as the called party number's NPA/NXX. After the call is handed off to a PSTN, the PSTN then routes the call through the network by consulting switch-based routing tables using the destination phone number (i.e., the called party's number).
In some cases, the destination phone number is not sufficient to make proper routing decisions, and one must ascertain the caller's location to appropriately determine how to route a call. By way of example and not by way of limitation, in the case of calls placed in an E9-1-1 system seeking emergency services, the destination phone number (“9-1-1”) does not uniquely map to a single public safety agency across the U.S. Instead, a 9-1-1 call maps to a specific Public Safety Answering Point (PSAP; sometimes also referred to as a Public Safety Answering Position) based on the caller's location. Such a caller location related routing in selecting a destination PSAP for a 9-1-1 call is not a problem if the caller is being served by a local switch where the mapping of “9-1-1” to the appropriate PSAP can be determined based on the originating phone number. For example, the NPA/NXX for the destination PSAP may be selected in such situations based upon the calling party's NPA/NXX.
A problem arises, however, in a VoIP network where a “centralized” switch can serve VoIP devices distributed over a broad geographic area and there is no fixed relationship between a caller's phone number (NPA/NXX) and the caller's location. As a result, communication networks operating using internet protocol (IP) cannot reliably route calls based upon the caller's location. Such IP network support for connecting geographically dispersed Voice over IP (VoIP) phone devices facilitates geographic portability of VoIP devices. For example, VoIP phones can be transported to any location, connected to the Internet, and calls may be completed from the new, often temporary, location. VoIP networks do not provide information regarding the geographic or geospatial location of callers. Location information is important, for example, when one needs to perform a service for a caller and may need to independently ascertain the caller's location without input from the caller. An example of such a situation is a special number call, such as a 9-1-1 emergency services call. Emergency service 9-1-1 calls will be employed herein as an exemplary embodiment of the present invention for purposes of illustration and explanation only and not for purposes of limiting the scope of the invention to special number calls only.
Voice over IP (VoIP) networks do not currently provide an accurate and reliable E9-1-1 solution. Using prior art technology, when a caller dials 9-1-1 on a VoIP network, the call is routed to the Public Switched Telephone Network (PSTN) by the VoIP switch using the calling party number of the user. The end office switch in the PSTN that locally serves the VoIP switch treats the call as an E9-1-1 call and passes it to a local E9-1-1 tandem (a specialized telecommunication switch for handling E9-1-1 call traffic). The E9-1-1 tandem queries its selective routing database (using the calling party number received) for the Public Safety Answering Point (PSAP) that has jurisdictional coverage for the caller. The E9-1-1 tandem then forwards the call to the identified PSAP over dedicated 9-1-1 trunks.
Such a straightforward prior art handling of calls suffices so long as the caller's location is within the same E9-1-1 tandem serving area as the VoIP switch. In VoIP networks, however, an IP phone in one part of the country (e.g. New York, N.Y.) can be served by a VoIP switch located in another part of the country (e.g. San Francisco, Calif.). Such operational portability creates problems vis-à-vis E9-1-1 call routing because, for example, the E9-1-1 tandem serving the VoIP switch in San Francisco will not recognize the caller's New York telephone number. That is, the E9-1-1 tandem serving the VoIP switch in San Francisco will not find the caller's New York telephone number in its selective routing tables, and thus will not be able to pass the call to the correct PSAP for providing emergency service for the caller in New York. Using prior art routing systems and techniques, the E9-1-1 tandem serving the VoIP switch in San Francisco will default route the call to a local PSAP in San Francisco. The San Francisco PSAP will be unable to dispatch appropriate emergency response to assist the caller in New York. The PSAP must verbally collect location information from the caller and try to determine the correct PSAP in New York appropriate for providing the needed emergency assistance. All the while, precious time is lost before an appropriate emergency response can be dispatched.
There is a need for a system and method for routing special number telephone calls involving an internet protocol network that facilitates routing of calls to a proper called party for providing appropriate response to the caller.